P0841: Transmission Fluid Pressure Sensor/Switch A Circuit Range/Performance

What does P0841 mean?

Transmission fluid pressure sensor/switch A and B are inputs inside the automatic gearbox. A switch only reports pressure present or absent, a sensor reports a value. The letter is the maker's choice: Allison 1000 uses A and B for the switches on shift valves S1 and S2, GM's CVT for the primary and secondary pulley sensors, GM's 2025 8-speed A for the lube pressure sensor; Ford reports pressure faults under its solenoid codes instead. P0841 means the signal is electrically fine but does not match the commanded state. GM's CVT sets it when pulley pressure misses its target by more than 500 kPa steady or 1500 kPa transient while the ratio is off by over 0.2 for about 6 s, type A. GM's 8-speed checks the lube sensor rises above 40 kPa after start-up; Mitsubishi's CVT sets it at 0.675 MPa deviation for 5 s.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine or transmission warning lamp on
• Shift shock, slipping or delayed engagement
• CVT: ratio and power limited

Common causes

• High Dirty or sticking valve, worn valve body
• High Pressure sensor or switch drifting or sticking
• Medium Fluid level low, fluid aged or filter clogged
• Medium Mechanical damage: thrust washer, CVT belt or pulley, pump
• Low Control module software

Likelihood is a general estimate across vehicles; your make and model may differ.